Preferred carrier selection method for selecting any available cellular carrier frequency when neither home nor preferred cellular carrier frequencies are available

ABSTRACT

A method and an apparatus for selecting a cellular carrier frequency for accessing cellular airtime services based upon a list of preferred system identification codes (SIDs). A cellular telephone is programmed to accept into memory a list of preferred SIDs corresponding to carriers through which service is preferred. While any SID remains in a preferred list, the standard A/B system selection function is replaced by a substitute system selection function which includes only three carrier selection modes including the Home Only mode, the SID Only mode, and a Roam Saver mode. With the Roam Saver carrier selection mode, the cellular telephone first prefers service through a home carrier and then through a carrier broadcasting a SID matching a SID on the preferred list, but never denies service to emergency or non-emergency destinations if any SID is detected. Status indicators are used to, among other purposes, differentiate between no service being available, service being available through a carrier broadcasting a home SID, a preferred SID, or a non-preferred available SID. Also, in addition to multiple number assignment modules (NAMs) being included to support subscriptions to services from multiple carriers, the user is provided the option of manually selecting which NAM is used or enabling the cellular telephone, through an auto-NAM function, to automatically select and use the NAM of any home carrier detected by the cellular telephone.

BACKGROUND OF THE INVENTION

The present invention relates generally to the field oftelecommunications, and more specifically, to the field of cellularcarrier selection.

A cellular telephone communication system typically provides services toan area by dividing the area into many smaller geographic areas, knownas cells, each of which is serviced by a transmitter-receiver station,known as a cell site. The cell sites are connected through landlines, orother communication links, to so-called mobile telephone switchingoffices (MTSO's) which are, in turn, connected to the public switchedtelephone network (PSTN). According to current FCC rules, any given areais serviced by up to two competing providers of cellular airtimecommunication services (i.e., cellular carriers). The two serviceproviders in any given geographic area, commonly referred to as "A" and"B" carriers, are assigned different groups of frequencies, or frequencysets, through which services are provided along paging, control, access,and voice channels, as would be understood by those reasonably skilledin the industry and as dictated by technical standards of appropriateregulatory agencies.

According to typical contemporary billing rate structures, distinctionsare made relative to whether or not the user has subscribed to airtimeservices with the carrier currently being accessed. If a call isoriginated within an area serviced by a carrier with which the callerhas a pre-existing billing arrangement such that a local telephonenumber has been assigned to the cellular telephone by that carrier, thecall can potentially be less expensive than a call made outside such aso-called "home" area, during which time the cellular telephone is saidto be "roaming" with respect to that carrier. A typical cellulartelephone contains memory locations known as a number assignment module(NAM) in which an installer technician stores an assigned telephonenumber and a system identification code (SID) which uniquely identifiesa particular carrier which is primarily intended to provide airtimeservice for that telephone. This carrier is referred to as the "home"carrier. Since each carrier broadcasts its unique SID in areas servicedby that carrier, a cellular telephone, in order to determine whether itis, at any given time, located within its home service area, typicallyscans certain frequencies to receive SIDs broadcast by the carriers andthen compares the received SIDs to SIDs stored in the NAM.

"A" frequencies are reserved for nonwireline carriers, while "B"frequencies are reserved for wireline carriers. Due at least in part toanticipated cooperation between similar types of carriers, conventionalcellular telephones enable users to choose among six carrier selectionmethods, commonly referred to as the standard A/B system selectionfeature. The six options include Prefer A, Prefer B, A Only, B Only,Home Only, and SID Only. According to the Prefer A option, the cellulartelephone prefers to use an "A" frequency before using a "B" frequency.The Prefer B option is similar in an opposite sense. Under the A Onlymode of operation, the cellular telephone uses only "A" frequencies, andconversely uses only "B" frequencies when operating under the B Onlymode. Under the Home Only mode, the cellular telephone is prohibitedfrom roaming, and under the SID Only mode, the cellular telephone can beused only when receiving one particular SID entered into memory by theuser.

Recently, "A" carriers and "B" carriers have been entering intocustomized roaming agreements whereby cellular telephones serviced byone of the agreeing carriers are able to operate at reduced rates inareas serviced by the other carrier. Unfortunately, the standard A/Bsystem selection options do not provide customized carrier selectionfunctions for any purpose, including supporting customized roamingagreements between carriers. One attempt at solving this problem isdisclosed in U.S. Pat. No. 4,916,728, issued to Blair. That patentdiscloses a carrier selection method which, when no SID matching thehome SID is received, allows normal operation only when a SID that doesnot exist on an exclusion list (or conversely exists on a "good" list)is received. A 911 override is also provided to allow dialing of certainemergency numbers if the only SID received is on the exclusion list.That method exhibits drawbacks by potentially denying available servicewhen both available SIDs are on the exclusion list or when the onlyavailable SID is on the exclusion list due to dead spots in, or gapsbetween, service areas. It is also unclear how the new mode of carrierselection affects the standard A/B system selection feature.

In addition, one type of cellular telephone, such as that disclosed inU.S. Pat. No. 5,020,091, issued to Krolopp et al., includes multipleNAMs for subscription to multiple carriers. In this way, the cellulartelephone owner can take advantage of potentially lower rates inmultiple geographically diverse areas by subscribing to carriers withineach service area. The telephone disclosed by the '091 patent furtherdiscloses means for prompting a user to choose to use a particular NAMwhen the cellular telephone is moved into an area serviced by a carrierwith which the user has been assigned a local number. Consequently, theuser is required to respond to such a prompt in order to benefit fromthe potentially more advantageous rates each time a new carrier islocationally "home" to the cellular telephone.

There is, therefore, a need in the industry for a system which addressesthese and other related, and unrelated, problems.

SUMMARY OF THE INVENTION

Briefly described, the present invention includes, in its most preferredembodiment, a method and an apparatus for selecting a cellular carrierfrequency for accessing cellular airtime services based upon a list ofpreferred SIDs. A cellular telephone is programmed to accept into memorya list of preferred, rather than "good", SIDs corresponding to carriersthrough which service will be preferred. When an installer technicianenters a SID into the preferred list, the standard A/B system selectionfunction is, while any S ID remains in the preferred list, replaced by asubstitute system selection function which includes only three carrierselection modes including the Home Only mode, the SID Only mode, and aRoam Saver mode. When the Roam Saver carrier selection mode is selectedby the user, while the cellular telephone will prefer service through acarrier broadcasting a SID matching a SID on the preferred list, thecellular telephone will never deny service to emergency or non-emergencydestinations if any SID, including one not on the preferred list, isreceived by the cellular telephone.

Status indicators are used to, among other purposes, differentiatebetween no service being available, service being available through acarrier broadcasting a SID matching a home SID (a home carrier), servicebeing available through a carrier broadcasting a SID matching a SID onthe preferred list (a preferred SID), and service being availablethrough a carrier broadcasting a SID not matching a home SID or a SID onthe preferred list (a non-preferred available SID). In the preferredembodiment, indicator lights are employed, while alternate embodimentsinclude status indicators taking the form of display icons, other lightsor lamps, display messages, audible tones, voice messages, etc.According to the preferred embodiment, carrier status indicators aresteady or intermittent depending on whether the detected SID is apreferred SID or a non-preferred SID, thus no indicator distinction ismade between detection of primary carriers (carriers of the A/B type ofthe first home carrier) and secondary carriers (carriers of the A/B typeopposite the first home carrier). Also, in addition to multiple NAMsbeing included to support subscriptions to services from multiplecarriers, the user is provided the option of manually selecting whichNAM is used or enabling the cellular telephone, through an auto-NAMfunction, to automatically select and use the NAM of any home carrierdetected by the cellular telephone.

It is therefore an object of the present invention to provide a methodand an apparatus for selecting a cellular carrier frequency foraccessing cellular airtime services based upon a list of preferred SIDs.

Another object of the present invention is to provide a method and anapparatus for providing a Roam Saver carrier selection mode in whichservice is never denied for either emergency or non-emergency calls whenany SID is detected.

Yet another object of the present invention is to provide a method andan apparatus for, through storing at least one SID in a preferred listmemory location, enabling a user to select a Roam Saver carrierselection mode in which service is never denied for either emergency ornon-emergency calls when any SID is detected, wherein the Roam Savercarrier selection option becomes unavailable when all SIDs are removedfrom the preferred list memory locations.

Still another object of the present invention is to provide a method andan apparatus for, through storing at least one SID in a preferred listmemory location, enabling a user to select among only three carrierselection options including a Roam Saver carrier selection mode forpreferably selecting carriers from a preferred list, a Home Only modefor selecting only home carriers, and SID Only mode for selecting only auser-defined carrier.

Still another object of the present invention is to provide a method andan apparatus for providing status indication to distinguish betweenpreferred carrier access and non-preferred carrier access.

Other objects, features and advantages of the present invention willbecome apparent upon reading and understanding the presentspecification, when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram representation of a cellular telephone capableof communicating with provider networks in accordance with the preferredembodiment of the present invention.

FIG. 2 is a chart of carrier selection priority levels withcorresponding status indicator configurations.

FIGS. 3-5 are flow chart representations of the steps of one method ofthe preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now in greater detail to the drawings in which like numeralsrepresent like components throughout the several views, FIG. 1 shows,among other elements, a block diagram representation of a cellulartelephone 10. With the exception of unique programming and memoryconfigurations and contents, the cellular telephone 10 of the preferredembodiment of the present invention is very similar to conventionalcellular telephones. An antenna 20 is shown connected through atransceiver 22 to a microprocessor-based logic control system 24 havingaccess to memory 26. Memory 26 is configured to contain programminginformation for directing operation of the cellular telephone, a memoryarea for receiving a list of preferred system identification codes(SIDs) from an installer technician, and multiple number assignmentmodules (NAMs) in which an installer technician stores, among otherinformation, SIDs corresponding to each provider of cellular airtimeservices with which the owner of the cellular telephone has subscribed.A conventional microphone 28, speaker 30, and key pad 32 are also shownconnected to the control system 24.

A set of status indicators 40 are also shown connected to the controlsystem 24 and include an in use indicator 42, a no service indicator 44,a roam A carrier indicator 46, and a roam B carrier indicator 48. Eitherroam A carrier indicator 46 or roam B carrier indicator 48 will beactivated to indicate the A/B carrier type of the system being accessedin a roaming condition. As is discussed below, roam indicator 46 or 48will light continuously when the cellular telephone 10 is roaming on acarrier whose SID is included in the preferred SID list, while roamindicator 46 or 48 will blink when the cellular telephone 10 is roamingon a carrier whose SID is not included on the preferred SID list.

The cellular telephone 10 is shown capable of communicating throughradio waves with both a primary carrier cell site 60 and a secondarycarrier cell site 70 of conventional cellular provider networks. Theprimary carrier cell site 60 provides service to a primary carrier cellcoverage area 62, and the secondary carrier cell site 70 providesservice to a secondary carrier cell coverage area 72. According to thispreferred embodiment, the primary carrier cell site 60 is shownconnected through landlines to a primary carrier mobile switching office(MTSO) 64 which is, in turn, connected through landline trunks to thepublic switched telephone network (PSTN) 66. Likewise, the secondarycarrier cell site 70 is connected through landlines to a secondarycarrier MTSO 74 which is, in turn, connected through landline trunks tothe PSTN 66.

The designation "primary" refers to the A/B system type of the carrierwhose SID is stored in the first NAM within memory 26, and thedesignation "secondary" refers to the other of the two A/B system types.Thus, the primary carrier cell site 60 communicates through frequencieswithin a frequency set designated for use by one of the A/B systemtypes, while the secondary carrier cell site 70 communicates throughfrequencies within a frequency set designated for use by the other A/Bsystem type. Thus, the frequency set designated for use by the primarycarrier is referred to herein as the primary (or home) frequency set,while the frequency set designated for use by the secondary carrier isreferred to herein as the secondary (or non-home) frequency set. Thedesignations "primary" and "secondary" may each, therefore, refer toeither "A" or "B" type carriers. According to FIG. 1, to be capable ofcommunicating with both the primary carrier cell site 60 and thesecondary carrier cell site 70, the cellular telephone 10 must belocated within the overlapping portion between the primary carrier cellcoverage area 62 and the secondary carrier cell coverage area 72.Furthermore, within any given service area for a carrier, one or morecarrier cell coverage areas 62, 72 are located adjacent to one anotherin conventional arrangement. However, due to a variety of factors, mostservice areas have holes caused by deadspots or gaps between cellcoverage areas. It is often the case that the other carrier within thatservice area is able to supply service within those holes.

Referring also to FIG. 2, which shows carrier selection priority levelswith configurations of the status indicators 40, the no serviceindicator 44 is shown to be off for every situation except that ofpriority level 7 where the cellular telephone 10 is unable to detect anySID from any carrier cell site 60, 70. In such a scenario, the roamindicators 46, 48 are also off. The in use indicator 42 is illuminatedwhenever a user attempts to access cellular service using the cellulartelephone 10. Also, in interpreting the chart of FIG. 2, it should beunderstood that with each lower priority level, (corresponding toincreasing priority numbers) SIDs of preceding higher priority levelsare not detectable.

If the cellular telephone 10 is located within a primary carrier cellcoverage area 62 and is able to receive signals from a primary carriercell site 60 broadcasting a SID corresponding to a SID stored as a homeSID in a NAM within the telephone 10, the carrier selection prioritylevel is priority level 1, the highest priority level. In such ascenario, the no service indicator 44 and both of the roam indicators46, 48 are off. Likewise, the status indicators 44, 46, 48 are also offduring a priority level 2 situation where the cellular telephone 10 islocated within a secondary carrier coverage area 72 and is able toreceive signals from a secondary carrier cell site 70 broadcasting a SIDcorresponding to a SID stored as a home SID in a NAM within thetelephone 10. Priority levels 3 or 4 occur when the cellular telephone10 is located to be able to detect a SID matching a SID on the preferredSID list within the memory 26 having been broadcast from a primary orsecondary carrier cell site 60 or 70, respectfully. Depending on whetherthe carrier is an "A" type or "B" type, and regardless of whether thecarrier is a primary or secondary carrier, either the roam A carrierindicator 46 or the roam B carrier indicator 48 will be continuouslyilluminated. During priority level 5 and 6 situations, the no serviceindicator 44 is also off, but the appropriate roam indicator 46 or 48 isintermittently illuminated. Priority levels 5 and 6 are reached when theonly SIDs detectable are not home SIDS or preferred SIDs. Thus, thesolid versus blinking distinction in the roam indicators 46 and 48designate the detection of preferred versus non-preferred availableSIDs.

It should be understood that in alternate embodiments of the presentinvention, the status indicators 40 include alternately constructed andoperated indicators 44, 46, 48. In one such alternate embodiment, theroam A and B carrier indicators 46, 48 are combined into one indicator,and in another alternate embodiment, a separate indicator is utilized toindicate whether or not an available SID is on the preferred list.Furthermore, it should be understood that the scanning and selectingsteps of the below preferred method are merely exemplary since manypossible equivalent sequences of search and selection operations may beutilized to determine carrier availability and select a carrier in anygiven area. Thus, the scope of the present invention is understood toinclude other methods for achieving the selection results and statusindicator configurations represented by the priority levels of FIG. 2.

Referring now also to FIGS. 3-5, flow chart representations show thesteps of the carrier selection method according to the preferredembodiment of the present invention. Before beginning the carrierselection process at step 100 in FIG. 3 or step 200 in FIG. 5, aninstaller enters at least one SID into an area in memory 26 (FIG. 1) tobegin a preferred list, thereby replacing the standard A/B systemselection function with a substitute system selection function whichallows a user to select from among only three carrier selection modesincluding the Home Only mode, the SID Only mode, and a Roam Saver mode.The standard A/B system selection function is enabled once more if allSIDs are removed from the preferred list. FIGS. 3 and 4 represent theRoam Saver mode, and FIG. 5 represents the Home Only and SID Only modes.When the Roam Saver carrier selection mode is selected by the user,while the cellular telephone 10 will prefer service through a carrierbroadcasting a SID matching a SID on the preferred list, the cellulartelephone 10 will never deny service to emergency or non-emergencydestinations if any SID, including one not on the preferred list, isdetected by the cellular telephone 10.

After the Roam Saver carrier selection process begins at step 100,internal flags and the status indicators 44, 46, 48 are initialized. Theinternal flags include PC-AVAIL and PC-PREF which are both set to NO;the no service indicator 44 is set to ON, and the roam carrierindicators 46, 48 are set to OFF. The PC-AVAIL (primary carrieravailable) flag is used to indicate whether any SID has been detectedduring a scan of the primary carrier frequencies, and the PC-PREF flag(primary carrier preferred) is used to indicate whether a SID matchingone on the preferred list has been detected during a scan of the primarycarrier frequencies. At step 104, the primary carrier frequencies arescanned to detect any SIDs being broadcast by primary carrier cell sites60. According to the preferred embodiment of the present invention, ifmore than one SID is detected during this monitoring of the primarycarrier frequencies, the SID received on the strongest signal is used.At decision 106, a decision is made as to whether a SID was detectedduring the scan of primary carrier frequencies. If a SID was notdetected, the process continues at connector 108 which transfers controlto the B connector 130 in FIG. 4, as is discussed below. On the otherhand, if a SID was detected, the process continues at decision 110 wherea determination is made as to whether the detected SID is a home SID. Asdiscussed above, such determination includes comparing the detected SIDto the home SIDs in all NAMs if the auto-NAM feature is enabled, andotherwise comparing the SID to the active NAM if the auto-NAM feature isdisabled.

If the detected SID matches a home SID, the process continues at step112 where the status indicators 44, 46, 48 are set and the cellulartelephone 10 is tuned to the frequency of the detected primary home SID.The process of tuning a cellular telephone 10 would be understood by onereasonably skilled in the industry. Setting of the indicators 44, 46, 48would follow that of priority level 1 shown in FIG. 2 wherein all of theindicators 44, 46, 48 are turned off. Finally, the process is terminatedat step 114. Periodically, and when a user actually attempts to place acall, the process is repeated to compensate for movement of the cellulartelephone 10. If the detected SID is not a home SID, the PC-AVAIL flagis set to YES at step 116. The detected SID is then compared to the SIDsin the preferred list at decision 118 to determined if the detected SIDis a preferred SID. If the detected SID is not a preferred SID, theprocess continues at connector 120 which transfers control to the Bconnector in FIG. 4, as is discussed below. Alternately, if the detectedSID is a preferred SID, the PC-PREF flag is set to YES at step 122, andthe process continues at connector 124 which also transfers control tothe B connector 130 in FIG. 4.

Referring to FIG. 4, after the B connector 130, the flow chartrepresentation shows that the frequencies of the secondary carrier arescanned for SIDs. If no SIDs are detected, the NO branch of the decision132 is taken to decision 134 which checks the PC-AVAIL flag. If thePC-AVAIL flag was not set earlier at step 116 in FIG. 3, the processcontinues at connector 136 which transfers control to the A connector140 in FIG. 3 where the process essentially begins again. On the otherhand, if the PC-AVAIL flag was set to YES, the process continues atconnector 144 which transfer control to the C connector 150 in FIG. 3.Referring back to FIG. 3, after the C connector 150, the primary carrierfrequencies are scanned again at step 152 to ensure that the carrierwhich supplied the SID previously detected on the primary carrier isstill available. If the SID is not detected at step 154, the NO branchis taken to restart the process, but if the SID was again detected onthe primary carrier, the YES branch is taken such that step 112 sets theindicators 44, 46, 48 and tunes the cellular telephone 10 to the primarycarrier detected. In this case, the indicators 44, 46, 48 are setaccording to priority level 3 or 5 of FIG. 2, depending on whether theprocess flowed through connector 124 or connector 120, respectively. Forexample, if the SID detected during the scan of the primary carrierfrequency set was on the preferred list, the process flowed through theconnector 124, and the indicators 44, 46, 48 are set according to thepriority level 3 of FIG. 2.

Referring back to FIG. 4, if SIDs are detected during the scan of thesecondary carrier frequency set, the YES branch of decision 132 istaken. At decision 160, like decision 110 of FIG. 3, it is determinedwhether the SID detected in step 13 1 is a home SID. If So, the YESbranch is taken to step 162 which sets the indicators 44, 46, 48according to priority level 2 of FIG. 2, and tunes the cellulartelephone 10 to the secondary carrier, after which the process isterminated at step 164. On the other hand, if the SID detected in step131 is not a home SID, the PC-PREF flag is checked at step 170 todetermine if a preferred SID was previously detected during the scan ofthe primary carrier frequency set. If so, the process continues atconnector 172 which also transfers control to the C connector 150 inFIG. 3. Once again if the primary carrier is still available (step 154in FIG. 3), the cellular telephone is tuned to the primary carrier, andthe indicators 44, 46, 48 set according to priority level 3 of FIG. 2.If the PC-PREF flag was not set, the NO branch of decision 170 is takento decision 174 which determines if the SID detected during the scan ofthe secondary carrier frequency set is a preferred SID. If so, the YESbranch is taken to step 162 which indicates that the cellular telephone10 is tuned to the secondary carrier and sets the indicators accordingto priority level 4 of FIG. 2. On the other hand, if the secondarycarrier SID is not a preferred SID, the PC-AVAIL flag is checked atdecision 176. If the PC-AVAIL flag is NO, the cellular telephone is setto the secondary carrier, and the status indicators 44, 46, 48 are setaccording to priority level 6 of FIG. 2. Alternatively, the processcontinues at connector 178 which also transfers control to the Cconnector 150 of FIG. 3 after which the cellular telephone 10 is tunedto the primary carrier, if available, and the indicators 44, 46, 48 areset according to priority level 5 of FIG. 2.

If the user selects the Home Only or SID Only modes of operation, thecarrier selection process proceeds according to the flow chart shown inFIG. 5 rather than those shown in FIGS. 3 and 4. The steps shown in FIG.5 are similar to the conventional Home Only and SID only carrierselection modes of the standard A/B system selection function. If theuser selects the SID Only mode of operation, the user is prompted toinput the desired SID into memory 26. If the user selects the Home Onlymode, the process will compare detected SIDs to all or individual NAMsdepending whether the auto-NAM feature is enabled by the user. After theprocess starts at step 200, the no service indicator 44 is turned on,and the roam carrier indicators 46, 48 are turned off. The primarycarrier frequency set is then scanned at step 204, and if any SIDs aredetected, the YES branch of decision 206 is taken to decision 208. Atdecision 208, depending on whether a Home Only or a SID Only mode isselected by the user, the detected SID is compared to a home SID or apreset user-defined SID, respectively. If the detected SID matches sucha home or set SID, the cellular telephone 10 is tuned to the primarycarrier, and the no service indicator 44 is turned off. Also, if the SIDOnly mode has been selected by the user, the appropriate roam indicator46, 48 is illuminated continuously, thus a SID entered by a user in theSID Only mode is treated as a preferred SID for illumination purposesaccording to the chart of FIG. 2. Subsequently, the process isterminated at step 212, and, like the process of FIGS. 3 and 4, theprocess of FIG. 5 is periodically, and when a user actually attempts toplace a call, repeated to compensate for movement of the cellulartelephone 10. If no SID is detected such that the NO branch of decision206 is taken, or if a detected SID causes the NO branch of decision 208to be taken, the process flows to step 214 which indicates that thesecondary carrier frequency set is scanned. If no SID is detected or ifa detected SID does not match a home or set SID, the process loops backto step 202. Otherwise, the cellular telephone 10 is tuned to thesecondary carrier, and the status indicators 44, 46, 48 set in a mannersimilar to step 210. Subsequently, the process is terminated at step222.

According to the preferred embodiment of the present invention, thepreferred SID list identifies providers associated with the provideridentified in the first NAM of memory 26. In other embodiments of thepresent invention, multiple preferred SID lists are included forassociation with each of the NAM's, and in still other embodiments, onelarge SID list with associations to different NAM's is utilized.

While the embodiments of the present invention which have been disclosedherein are the preferred forms, other embodiments of the presentinvention will suggest themselves to persons skilled in the art in viewof this disclosure. Therefore, it will be understood that variations andmodifications can be effected within the spirit and scope of theinvention and that the scope of the present invention should only belimited by the claims below.

We claim:
 1. A method for selecting a cellular carrier frequency for accessing cellular airtime services, said method comprising the steps of:defining at least one predefined home system identification code (SID) and at least one predefined preferred SID; monitoring a plurality of frequencies to detect any SID corresponding to any frequency of the plurality of frequencies, including steps ofmonitoring a plurality of primary carrier frequencies to detect any SID corresponding to any frequency of the plurality of primary carrier frequencies, and monitoring a plurality of secondary carrier frequencies to detect any SID corresponding to any frequency of the plurality of secondary carrier frequencies; selecting a frequency, for calls to ordinary telephone numbers, corresponding to a SID matching said predefined home SID if the SID matching said predefined home SID is detected, including steps ofselecting a primary carrier frequency corresponding to the SID matching said predefined home SID if the SID matching said predefined home SID is detected upon the primary carrier frequency, and selecting a secondary carrier frequency corresponding to the SID matching said predefined home SID if the SID matching said predefined home SID is detected upon the secondary carrier frequency and the SID matching said predefined home SID is not detected upon any primary carrier frequency; selecting a frequency, for-calls to ordinary telephone numbers, corresponding to a SID matching said predefined preferred SID ifthe SID matching said predefined preferred SID is detected and no SID matching said predefined home SID is detected; and selecting a frequency, for calls to ordinary telephone numbers, corresponding to a SID not matching either said predefined home SID or said predefined preferred SID ifthe SID not matching either said predefined home SID or said predefined preferred SID is detected and no SID matching either said predefined home SID or said predefined preferred SID is detected.
 2. The method of claim 1, wherein the step of monitoring the plurality of frequencies includes, at least, the steps ofdesignating a plurality of carrier frequencies as primary carrier frequencies by determining a carrier type of a SID stored in an initial number assignment module, and designating a remaining plurality of carrier frequencies as secondary carrier frequencies in response to the step of designating the plurality of carrier frequencies as primary carrier frequencies.
 3. The method of claim 1, wherein the step of selecting the frequency corresponding to a SID matching said predefined preferred SID includes, at least, the steps ofselecting a primary carrier frequency corresponding to the SID matching said predefined preferred SID ifthe SID matching said predefined preferred SID is detected upon the primary carrier frequency, and no SID matching said predefined home SID is detected on any frequency, and selecting a secondary carrier frequency corresponding to the SID matching the predefined preferred SID ifthe SID matching said predefined preferred SID is detected upon the secondary carrier frequency, no SID matching said predefined home SID is detected on any frequency, and no SID matching said predefined preferred SID is detected upon any primary carrier frequency.
 4. The method of claim 3, wherein the step of selecting the frequency corresponding to a SID not matching either said predefined home SID or said predefined preferred SID includes, at least, the steps ofselecting a primary carrier frequency corresponding to a SID not matching either said predefined home SID or said predefined preferred SID ifthe SID not matching either said predefined home SID or said predefined preferred SID is detected upon a primary carrier frequency, and no SID matching either said predefined home SID or said predefined preferred SID is detected on any frequency, and selecting a secondary carrier frequency corresponding to a SID not matching either said predefined home SID or said predefined preferred SID ifthe SID not matching either said predefined home SID or said predefined preferred SID is detected upon the secondary carrier frequency, no SID matching either said predefined home SID or said predefined preferred SID is detected on any frequency, and no SID is detected upon any primary carrier frequency.
 5. The method of claim 1, wherein the step of selecting the frequency corresponding to a SID matching said predefined home SID includes, at least, the step of comparing any detected SID to a plurality of predefined home SIDs.
 6. The method of claim 5, wherein the step of selecting the frequency corresponding to a SID matching said predefined home SID further includes, at least, the step of automatically selecting a frequency corresponding to a first SID matching the predefined home SID from the plurality of predefined home SIDs.
 7. The method of claim 5, wherein the step of comparing any detected SID to the plurality of predefined home SIDs is responsive to selective user enablement.
 8. The method of claim 1, wherein the step of selecting the frequency corresponding to a SID matching said predefined preferred SID is responsive to selective enablement.
 9. The method of claim 8, wherein the selective enablement includes entering at least one predefined preferred SID into a memory device.
 10. The method of claim 9, wherein the selective enablement further includes selective user enablement.
 11. The method of claim 1, further comprising the steps of defining at least one user-defined SID, and selecting the frequency corresponding to a SID matching said user-defined SID if the SID matching said user-defined SID is detected, wherein all of the selecting steps are responsive to being selectively user enabled, and wherein the method further comprises the step of providing a user with an opportunity of choosing between only three carrier selection modes consisting ofa roam saver mode wherein all the selecting steps are enabled, a home only mode wherein only the step of selecting a frequency corresponding to a SID matching said predefined home SID is enabled, and a SID only mode wherein only the step of selecting a frequency corresponding to a SID matching said user-defined SID is enabled.
 12. The method of claim 1, further comprising the step of activating a no service indicator only if no SID is detected.
 13. The method of claim 1, further comprising the steps ofactivating neither a roam status indicator nor a no service indicator if a frequency corresponding to a SID matching said predefined home SID is selected; continuously activating a roam status indicator if a frequency corresponding to a SID matching said predefined preferred SID and not matching said predefined home SID is selected; intermittently activating a roam status indicator if a frequency corresponding to a SID not matching either said predefined home SID or said predefined preferred SID is selected; and activating a no service indicator only if no SID is detected.
 14. A cellular carrier frequency selection apparatus comprising:detecting means for monitoring a plurality of frequencies to detect any system identification code (SID) corresponding to any frequency of said plurality of frequencies, wherein said detecting means includes, at least,primary means for monitoring a plurality of primary carrier frequencies to detect any SID corresponding to any frequency of said plurality of primary carrier frequencies, and secondary means for monitoring a plurality of secondary carrier frequencies to detect any SID corresponding to any frequency of said plurality of secondary carrier frequencies; and analyzing means associated with said detecting means for analyzing any SID detected by said detecting means and for selecting a frequency for use with calls, said analyzing means including, at least,memory means for defining at least one predefined home SID and at least one predefined preferred SID, home selecting means for selecting a frequency, for calls to ordinary telephone numbers, corresponding to a SID matching said predefined home SID if the SID matching said predefined home SID is detected, wherein said home selecting means includes, at least,primary home selecting means for selecting a primary carrier frequency corresponding to the SID matching said predefined home SID if the SID matching said predefined home SID is detected upon the primary carrier frequency, and secondary home selecting means for selecting a secondary carrier frequency corresponding to the SID matching said predefined home SID if the SID matching said predefined home SID is detected upon the secondary carrier frequency and the SID matching a predefined home SID is not detected upon any primary carrier frequency, preferred selecting means for selecting a frequency, for calls to ordinary telephone numbers, corresponding to a SID matching said predefined preferred SID ifthe SID matching said predefined preferred SID is detected and no SID matching said predefined home SID is detected, and remainder selecting means for selecting a frequency, for calls to ordinary telephone numbers, corresponding to a SID not matching either said predefined home SID or said predefined preferred SID ifthe SID not matching either said predefined home SID or said predefined preferred SID is detected and no SID matching either said predefined home SID or said predefined preferred SID is detected.
 15. The apparatus of claim 14, wherein said preferred selecting means includes, at least,primary preferred selecting means for selecting a primary carrier frequency corresponding to the SID matching said predefined preferred SID ifthe SID matching said predefined preferred SID is detected upon the primary carrier frequency, and no SID matching said predefined home SID is detected, and secondary preferred selecting means for selecting a secondary carrier frequency corresponding to the SID matching said predefined preferred SID ifthe SID matching said predefined preferred SID is detected upon said secondary carrier frequency, no SID matching said predefined home SID is detected, and no SID matching said predefined preferred SID is detected upon any primary carrier frequency.
 16. The apparatus of claim 15, wherein said remainder selecting means includes, at least,primary remainder selecting means for selecting a primary carrier frequency corresponding to the SID not matching either said predefined home SID or said predefined preferred SID ifthe SID not matching either said predefined home SID or said predefined preferred SID is detected upon the primary carrier frequency, and no SID matching either said predefined home SID or said predefined preferred SID is detected, and secondary remainder selecting means for selecting a secondary carrier frequency corresponding to the SID not matching either said predefined home SID or said predefined preferred SID ifthe SID not matching either said predefined home SID or said predefined preferred SID is detected upon the secondary carrier frequency, no SID matching either said predefined home SID or said predefined preferred SID is detected, and no SID not matching either said predefined home SID or said predefined preferred SID is detected upon any primary carrier frequency.
 17. The apparatus of claim 14, wherein said home selecting means includes, at least, a multiple analysis means for comparing any detected SID to a plurality of predefined home SIDs.
 18. The apparatus of claim 17, wherein said multiple analysis means includes, at least, an automatic means for automatically selecting a frequency corresponding to a first SID matching the predefined home SID from said plurality of predefined home SIDs.
 19. The apparatus of claim 17, wherein said multiple analysis means includes, at least, a selective means for selectively activating said multiple analysis means.
 20. The apparatus of claim 14, wherein said preferred selecting means includes, at least, a responsive means for enabling said preferred selecting means.
 21. The apparatus of claim 20, wherein said responsive means includes, at least, means for enabling said preferred selecting means upon entering at least one predefined preferred SID into a memory device.
 22. The apparatus of claim 21, wherein said preferred selecting means further includes, at least, a user disabling means for selectively disabling said preferred selecting means without deleting all SIDs from said memory device.
 23. The apparatus of claim 14, further comprising a mode means for providing a user with an option of choosing between only three carrier selection modes for enabling said selecting means, said mode means including, at least,a roam saver mode means for enabling all selecting means of said analyzing means, a home only mode means for enabling said home selecting means and disabling said preferred selecting means and said remainder selecting means, wherein only SIDs matching said predefined home SID are selected, and a SID only mode means for disabling said home selecting means, said preferred selecting means, and said remainder selecting means and for providing said analyzing means with a SID only selecting means for selecting a frequency corresponding to a SID matching a predefined SID if a SID matching said predefined SID is detected.
 24. The apparatus of claim 14, further comprising means for activating a no service indicator only if no SID is detected.
 25. The apparatus of claim 14, further comprising display means for displaying carrier selection including, at least,home display means for activating neither a roam status indicator nor a no service indicator if a frequency corresponding to a SID matching said predefined home SID is selected; preferred display means for continuously activating a roam status indicator if a frequency corresponding to a SID matching said predefined preferred SID and not matching said predefined home SID is selected; remainder display means for intermittently activating a roam status indicator if a frequency corresponding to a SID not matching either said predefined home SID or said predefined preferred SID is selected; and no service means for activating a no service indicator only if no SID is detected.
 26. A method for selecting a cellular carrier frequency for accessing cellular airtime services, said method comprising the steps of:defining at least one predefined home system identification code (SID) and at least one predefined preferred SID; monitoring a plurality of frequencies to detect any SID corresponding to any frequency of the plurality of frequencies, including steps ofdesignating a plurality of carrier frequencies as primary carrier frequencies by determining a carrier type of a SID stored in an initial number assignment module, designating a remaining plurality of carrier frequencies as secondary carrier frequencies in response to the step of designating the plurality of carrier frequencies as primary carrier frequencies, monitoring the plurality of primary carrier-frequencies to detect any SID corresponding to any frequency of the plurality of primary carrier frequencies, and monitoring the plurality of secondary carrier frequencies to detect any SID corresponding to any frequency of the plurality of secondary carrier frequencies; selecting a frequency, for calls to ordinary telephone numbers, corresponding to a SID matching said predefined home SID if the SID matching said predefined home SID is detected; selecting a frequency, for calls to ordinary telephone numbers, corresponding to a SID matching said predefined preferred SID ifthe SID matching said predefined preferred SID is detected and no SID matching said predefined home SID is detected; and selecting a frequency, for calls to ordinary telephone numbers, corresponding to a SID not matching either said predefined home SID or said predefined preferred SID ifthe SID not matching either said predefined home SID or said predefined preferred SID is detected and no SID matching either said predefined home SID or said predefined preferred SID is detected.
 27. The method of claim 26, wherein the step of selecting the frequency corresponding to a SID matching a predefined home SID includes, at least, the steps ofselecting a primary carrier frequency corresponding to the SID matching said predefined home SID if the SID matching said predefined home SID is detected upon the primary carrier frequency, and selecting a secondary carrier frequency corresponding to the SID matching said predefined home SID if the SID matching said predefined home SID is detected upon the secondary carrier frequency and the SID matching said predefined home SID is not detected upon any primary carrier frequency.
 28. The method of claim 27, wherein the step of selecting the frequency corresponding to a SID matching said predefined preferred SID includes, at least, the steps ofselecting a primary carrier frequency corresponding to the SID matching said predefined preferred SID ifthe SID matching said predefined preferred SID is detected upon the primary carrier frequency, and no SID matching said predefined home SID is detected on any frequency, and selecting a secondary carrier frequency corresponding to the SID matching the predefined preferred SID ifthe SID matching said predefined preferred SID is detected upon the secondary carrier frequency, no SID matching said predefined home SID is detected on any frequency, and no SID matching said predefined preferred SID is detected upon any primary carrier frequency.
 29. The method of claim 28, wherein the step of selecting the frequency corresponding to a SID not matching either said predefined home SID or said predefined preferred SID includes, at least, the steps ofselecting a primary carrier frequency corresponding to a SID not matching either said predefined home SID or said predefined preferred SID ifthe SID not matching either said predefined home SID or said predefined preferred SID is detected upon a primary carrier frequency, and no SID matching either said predefined home SID or said predefined preferred SID is detected on any frequency, and selecting a secondary carrier frequency corresponding to a SID not matching either said predefined home SID or said predefined preferred SID ifthe SID not matching either said predefined home SID or said predefined preferred SID is detected upon the secondary carrier frequency, no SID matching either said predefined home SID or said predefined preferred SID is detected on any frequency, and no SID is detected upon any primary carrier frequency.
 30. The method of claim 26, wherein the step of selecting the frequency corresponding to a SID matching said predefined home SID includes, at least, the step of comparing any detected SID to a plurality of predefined home SIDs.
 31. The method of claim 30, wherein the step of selecting the frequency corresponding to a SID matching said predefined home SID further includes, at least, the step of automatically selecting a frequency corresponding to a first SID matching the predefined home SID from the plurality of predefined home SIDs.
 32. The method of claim 30, wherein the step of comparing any detected SID to the plurality of predefined home SIDs is responsive to selective user enablement.
 33. The method of claim 26, wherein the step of selecting the frequency corresponding to a SID matching said predefined preferred SID is responsive to selective enablement.
 34. The method of claim 33, wherein the selective enablement includes entering at least one predefined preferred SID into a memory device.
 35. The method of claim 34, wherein the selective enablement further includes selective user enablement.
 36. The method of claim 26, further comprising the steps of defining at least one user-defined SID, and selecting the frequency corresponding to a SID matching said user-defined SID if the SID matching said user-defined SID is detected, wherein all of the selecting steps are responsive to being selectively user enabled, and wherein the method further comprises the step of providing a user with an opportunity of choosing between only three carrier selection modes consisting ofa roam saver mode wherein all the selecting steps are enabled, a home only mode wherein only the step of selecting a frequency corresponding to a SID matching said predefined home SID is enabled, and a SID only mode wherein only the step of selecting a frequency corresponding to a SID matching said user-defined SID is enabled.
 37. The method of claim 26, further comprising the step of activating a no service indicator only if no SID is detected.
 38. The method of claim 26, further comprising the steps ofactivating neither a roam status indicator nor a no service indicator if a frequency corresponding to a SID matching said predefined home SID is selected; continuously activating a roam status indicator if a frequency corresponding to a SID matching said predefined preferred SID and not matching said predefined home SID is selected; intermittently activating a roam status indicator if a frequency corresponding to a SID not matching either said predefined home SID or said predefined preferred SID is selected; and activating a no service indicator only if no SID is detected. 